Delayed action magnetic circuit breaker



p 1954 K. w. WILCKENS DELAYED ACTION MAGNETIC CIRCUIT BREAKER Filed Dec. 7, 1950 INVENTOR 37 I KURT W- WILCKEN5 HIS ATTORNEY Patented Sept. 28, 1954 TENT OFFICE DELAYED ACTION MAGNETIC CIRCUIT BREAKER Kurt W. Wilckens, Morrisville, Pa., assignor to Heinemann Electric Company, Trenton, N. 3., a corporation of New Jersey Application December 7, 1950, Serial No. 199,597

8 Claims.

My invention is an improved circuit breaker of the type in which a switch blade has operatively associated therewith an electromagnetic trip mechanism having an armature attracted, on overload, by an electro-magnet, and the leading object of my invention is to increase the effectiveness of the electro-magnet.

In accordance with my invention, the electromagnet comprises a solenoid coil and magnetically permeable members in the magnetic field of the coil and normally separated from one another by a gap or gaps, one or more of which are automatically closed on overload to produce an electro-magnet having adjacent poles of opposite polarity for attracting the armature of the trip mechanism. On a given current flow through the coil, the attraction of the armature, when the gaps are so closed that the members form a closed U-magnet, is approximately eleven times the attraction that is exerted when the gaps are open, thereby insuring adequate power to insure the operation of a tripping mechanism upon the occurrence of an overload or permitting a decrease in the number of ampere turns in the coil.

The gap closer preferably consists of a pistonlike plunger or core having a flanged head and enclosed in a tube or dash pot of non-magnet izable material, within the electro-magnetic coil, so that the movements of the core in response to the pull of the magnetic field are retarded to a desired degree before making contact with the permeable members.

The principles of my invention and the best mode in which I have contemplated putting such principles into practice will further appear from the following description and the accompanying drawings in illustration thereof.

In the drawings, Fig. 1 is a part sectional side elevation of a circuit breaker embodying my invention; Fig. 2 is a detached longitudinal sectional view of the electro-magnetic mechanism with the gaps closed; Fig. 3 is a transverse sectional view taken on the line 33 of Fig. 2; Fig. 4 is a transverse sectional View taken on the line 44 of Fig. 2; Fig. 5 is a detached, fragmentary, sectional view showing a, modification of the electro-magnetic mechanism; and Fig. 6 is a detached, fragmentary sectional view showing a further modification of the electro-magnetic mechanism.

As illustrated in the drawings, my invention is embodied in a circuit breaker comprising a magnetically permeable L-shaped frame having a leg I secured by a bolt 2 to the insulating base 3 of a casing I.

A non-magnetic tube 5 is seated in and bushes an aperture 6 in the leg I and forms a dash-pot chamber I on one side of the leg. The chamber I communicates through an aperture 6 in the leg with a chamber 9 formed on the other side of the leg by a non-magnetic tubular cap It soldered to the leg coaxially with the tube 5 and spaced radially from the periphery of the aperture 6 so as to leave a surface I3 of the leg I exposed within the cap.

As shown in Figs. 1 to 5, the outer end of the tube 5 is sealed by pole piece I I having a surface I2 exposed within the chamber 1.

A magnetically permeable, soft iron plunger I4 is housed in the chambers I and 9 and has a flanged head I5 movable into direct contact with the exposed surface I3. It will be noted that the tube 5 forms a non-magnetic spacer or bushing between the plunger I4 and the Wall of the aperture 6 so as to minimize any drag on the plunger while moving through the frame leg I, and that contact between the plunger I l and frame leg I occurs only when the head I5 contacts the exposed face I3 of the frame between the edge of the aperture 6 and the tube I0 spaced radially therefrom.

The core I4 has a reduced nose Ma. which as shown in Figs. 1 to 4, is movable into direct contact with the surface I2 to establish a metallic flux path between the frame leg I and the pole piece I I. The nose and head are normally biased away from the respective surfaces I2 and I3 by a coiled spring I6 interposed between the pole piece I I and plunger I4 and encircling the nose Ida.

The inner surface of the cap I6 is provided with ribs or serrations I! to preclude any tendency of the head I5 to adhere thereto by suction.

A solenoid coil I8 is wound on the tube 5 between the washers I9 and 20 respectively abutting the leg I and the pole piece II and has one end connected by a lead 2| with a load terminal (not shown) and its other end connected by a pig tail 22 with a movable switch blade 23 pivotally mounted on the ears 24 of the frame. The frame has a magnetically permeable leg I formed integrally with the leg I and extending transversely thereto along the solenoid coil I8 so that its forward end 26 forms a pole piece complementary to the pole piece I I.

An armature 27, adapted to bridge the pole pieces II and 2B, is pivotally mounted on the ears 28 of the frame and has a curved finger 29 extending along the leg I and rockable by the movement of the armature 21 into engagement with a latch member 30 for unlatching the toggle formed by the links 3I and 32 connecting 3 the switch blade 23 with an operating handle 34 mounted on the ears 28, as more fully set forth in my Letters Patent No. 2,360,922.

When the toggle links are latched rigidly together, the rocking of the handle 34 moves the switch blade 23 into engagement with a fixed contact 35 connected with the line terminal 36. The blade 23 is normally biased away from the contact 35 by a spring 3! whenever the toggle links are unlatched by the rocking of the member 30 or whenever the handle 34 is turned on its pivot to the off position.

When the switch blade 23 is in engagement with the contact 35, current flows from the line terminal 36 through the contact 35, blade 23, pig tail 22, solenoid coil [8 and the lead 21 to the load terminal. The nose [4a is at all times within the magnetic field of the solenoid coil l8, but so long as the current does not exceed a predetermined overload, say 125% of rated capacity, the coiled spring l6 exerts a force suincient to overcome the pull of the magnetic flux on the core 14 and keep the head l5 retracted against the ridges I! (Fig. 1).

When, however, an overload in excess of the predetermined minimum fiows through the solenoid coil l8, its magnetic fiux causes the core 4 to move toward the pole piece ll against the action of the spring [6 and against the retarding action of liquid or air 31 in the chambers 1 and 9. The time lag imposed by the dash-pot action will vary proportionately to the degree of overload. When the overload is at a minimum above the predetermined permissible amount, the

core It will continue to move forward until its will be generated which will cross the diminishing gap between the plunger nose Ma and the exposed surface 12 and will cross the gap formed by the tube 5 between the plunger l4 and leg I, and cause the pole pieces II and 26 to attract the armature 2'? before the gaps are completely I closed.

If there should be a short circuit, the magnetic flux generated by the coil l8 will be sufficient to instantly rock the armature 21.

The movement of the armature 21 toward the pole piece Ii lifts the finger 29 which rocks the latch member 38 and unlatches the toggle formed by the links 3!, 32, thereby permitting the spring 3! to move the blade 23 away from the contact 35.

When a flux density lower than that resulting from the double contact of the plunger 14, as shown in Figs. 1 to 4, will satisfactorily operate the armature 21, the structure may be modified as shown in Figs. 5 and 6.

As shown in Fig. 5, the nose of the plunger I4 may be so shortened as to leave a slight gap between its tip and the surface I2 of the pole piece H and thereby avoid hammering on or displacement of the pole piece. The gap produces a certain reluctivity into the magnetic circuit, but the contact or the head 15 with the frame section [3 will result in a flux density at the pole pieces II and 12 substantially as great as though the core contacted the pole piece surface 12 and was 4 separated throughout from the frame I by the tube 5.

As shown in Fig. 6, the tube 5 may have an integral end and body of non-magnetizable material, as brass. When the head 15 contacts the frame surface E3, the tip of the plunger nose will be adjacent to or in contact with the end of the tube and flux will flow from the tip of the core through the tube end, across the air gap, through the armature, and across the air gap to the pole 26, thereby attracting the armature.

Having described my invention, I claim:

1. In a device of the character described, the combination of an armature and an electromagnet in operative association with said armature and including a coil, an apertured, magnetizable frame in the magnetic field of said coil, a sealed retarding dash-pot having tubular walls of non-magnetizable material projecting oppositely from said frame and surrounding the aperture therein, said frame having a section adjacent to said aperture exposed within said dashpot, and a core movable longitudinally in said dash-pot and having a magnetically permeable member movable into contact with said exposed section to close a gap in a magnetic circuit and abnormally increase the flux attracting said armature.

2. In a device of the character described, the combination of an armature and an electromagnet in operative association with said armature and including a coil, an apertured, magnetizable frame in the magnetic field of said coil, a sealed retarding dash-pot having tubular walls of non-magnetizable material projecting oppositely from said frame, one of said tubular walls forming a bushing in said frame aperture, said frame having an exposed section within said dash-pot, and a core movable longitudinally in said dash-pot and having a flange movable into contact with said exposed section of said frame.

3. In a device of the character described, the combination of a solenoid coil having a pole piece adjacent to one end thereof, a magnetically permeable member having a part extending along the exterior of said coil and forming a pole piece, said pole piece and member normally having multiple gaps between them, a magnetically permeable member within the magnetic field of said core and movable thereby into direct contact with both said pole piece and first named member to close a gap between them, a non-magnetic sleeve encircling said movable member throughout its length and an armature operatively associated with said pole pieces and attracted thereby and shortening a gap between them.

4. In a device of the character described, the combination of a magnetically permeable frame having transverse legs, non-magnetic walls forming chambers on opposite sides of one of said legs, a solenoid coil surrounding one of said chambers and extending along a leg of said frame, a pole piece at one end of said last named chamber, said frame and pole piece having surfaces exposed in said chambers, a magnetically permeable plunger sealed in said chambers movable in said chambers by magnetic flux of said coil toward said exposed surfaces of said pole piece and frame, and an armature in operative association with said pole piece and frame.

5. In a device of the character described, the combination of a solenoid coil, non-magnetic walls forming sealed communicating chambers within and without said coil, a pole piece at one end of said coil and having a wall exposed in one of said chambers, a magnetically permeable member extending along the exterior of said coil and having a section forming a pole piece complementary to said pole piece first named and a section having a wall exposed in one of said chambers, and a magnetically permeable plunger having an enlarged portion and in said chambers and movable by the magnetic flux of said coil toward contact with both of said exposed surfaces.

6. In a device of the character described, a magnetically permeable frame having transverse legs, tubes forming sealed communicatin chambers on opposite sides of one of said legs and communicating therethrough, a solenoid coil encircling one of said tubes, a pole piece at the end of said coil, and a magnetically permeable plunger in said chambers and having a nose movable toward said pole piece and a head movable into direct contact with said first named leg to close gaps in a magnetic circuit, a spring tending to bias said plunger nose and head away from said pole piece and leg respectively, and an armature movable toward said pole piece and frame by magnetic flux abnormally increased by closure of said gaps.

7. In a device of the character described, a magnetically permeable frame containing an aperture, a sealed retarding dash pot including a non-magnetic tube seated in said aperture and a tube secured to said frame and radially spaced from the edge of said aperture so as to leave a surface of said frame exposed within said last named tube, a magnetically permeable plunger in said tubes and having a flange movable into contact with said exposed surface to close a gap in a magnetic circuit, and a solenoid coil encircling said first named tube.

8. In a device of the character described, the combination of a sealed dash pot having a magnetically permeable member forming a pole piece, an electromagnetic coil encircling said dash pot adjacent to said pole piece, a magnetically permeable frame in the field of said coil and hav ing a member forming a pole piece complementary to but of opposite polarity from said first named pole piece, an armature in the field of said pole pieces and normally spaced therefrom but attracted thereby upon the flow of current through said coil, and a magnetically permeable core movable in and retarded by said dash pot and having an enlarged portion, said core being movable into magnetic contact with said first named pole piece and with said frame and said armature being movable into magnetic contact with said pole pieces upon the flow of abnormal current through said coil.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,194,132 Brown Aug. 8, 1916 1,330,094 Simon Feb. 10, 1920 1,354,883 Canfield Oct. 5, 1920 2,121,657 Fisher June 21, 1938 2,200,109 Wilckens May 7, 1940 2,360,922 Wilckens Oct. 24, 194.4 2,391,277 Stapleton Dec. 18, 1945 

